The assignee of the present invention manufactures and deploys spacecraft for communications and broadcast services. Such spacecraft commonly include various appendages, such as, for example, antenna reflectors, that may need to be deployable and/or steerable after the spacecraft is deployed on orbit. It is known in the art to provide an antenna positioning mechanism (APM), for example, to enable the appendage to be rotated with respect to the spacecraft about one or more axes for deployment and/or steering. On orbit, therefore, the APM may be the primary, or only, mechanical interface between the appendage and the spacecraft. Such mechanisms, however, are not commonly able to withstand launch environments when loaded with the appendage. Instead, hold-down mechanisms are conventionally provided which support the appendage during launch. Once the spacecraft has achieved orbit, the hold-down mechanism is “released” by, for example, severing a mechanical rod or bolt attaching the hold-down mechanism to the appendage, or by actuating a non-pyrotechnic release device such as that described in U.S. Pat. No. 6,133,818, to Hsieh, et al., assigned to the assignee of the present invention, and incorporated by reference herein in its entirety. Once the hold-down mechanism is released, the APM is enabled to deploy and/or steer the reflector or other appendage.
An example of a conventional hold-down mechanism 100 is illustrated in FIG. 1. Mechanism 100 includes frame 101 that may be attached to a spacecraft (not shown) by way of hinges 103. Prior to release of the hold-down mechanism, an attachment member 110 of a spacecraft appendage (not shown) is secured to the spacecraft by hold-down mechanism 100. Rod 105, for example may connect attachment member 110 to frame 101. When hold-down mechanism 100 is to be released, release device/cutter 106 releases or severs rod 105, thereby permitting attachment member 110 and the spacecraft appendage to be deployed away (vertically, in the illustrated view) from the hold-down mechanism 100. Thereafter, frame 101 may be retracted by rotating frame 101 about an axis of hinges 103 so that frame 101 is folded against a sidewall of the spacecraft, thereby expanding the range of motion available to the spacecraft appendage.